Photo printing process



Oct. 16, 1956 F. G. BILHOEFER 2,757,093

PHOTO PRINTING PROCESS Filed June 23, 1950 2 Sheets-Sheet l 776.4. 4 llIHIHHHHIIIIIIIIIIIE F16" nmmun v F/Ci/Q- I, Hm

I EfMSP/CK 5/1 #05/58.

INVENTOR.

Oct-16,1956 F. ,G. BILHOEFER 2,757,093

mom PRINTING PROCESS Filed June 23, 1950 2 Sheets-Sheet 2 Git in t states Serial No.

SClaims. ((1 95 -8l} Application June 23, 1959,

This invention relates to a new and improved method of preparing continuous tone illustrations, such as wash drawings or photographs, for reproduction by printing plates as are used in the various photo-mechanical printing processes known as lithography, offset printing, photo engraving, said the like; and to the means employed and the printing plates produced. These plates may be either line plates, half-tone plates, or combination line and half-tone plates characterized by masking, stripping, etc. This application is a continuation-in-part of my patent application Ser. No. 587,127, tiled April 7, i945, now abandoned.

it is the purpose of this invention to render the gradations of tone values of the original upon the plate in different and distinct designs or patterns, such as a formation of dots for the light tones, a series of parallel lines for the medium tones, and a so-called cross-hatch for the dark tones, and also to provide clear portions for the high lights and solid color patches for the deepest shadows or blacks.

In the past, reproduction requirements have been met by methods well known in the art. For reproduction by so-called half-tone plates, the continuous tone illustration or object usually is photographed in a camera through a crosslined glass screen, used at varied distance from the sensitized surface, employing correspondingly different lens-apertures for the recording or the lighter and darker tones, thereby producing a pattern of dots of varied size, that is, small dots for the lighter tones and increasingly larger dots for the darker tones. A number of variations and improvements of this process are known, producing essentially the same result, that is, one pattern, usually dots, accentuated in the darker tones and diminished in the lighter tones. Clear highlights are produced by hand work or elaborate processes, such as the drop out half-tone negative process described in Patent 2,315,101.

For reproduction by so-called line plates, usually an artist is employed to make a drawing of the subject in pen and ink, obtaining graded effects through stippling with dots, through varied spacing or" lines or through the use of rough drawing papers, which break up the lines or tones into irregular dots, lines or other areas, each part of which will rint black or other desired solid color. A number or" semi-mechanical labor saving devices are available for this purpose, such as the Ben Day tones, the Hutchinsons artists shading mediurns, scratch-boards, Ross papers, Draft tints, and others. Some of these are available in single and double patterns. All of these methods still necessitate such artists handwork in blocking out or laying in of the separate tones or tints. The ima e thus resolved into lines or other pattern is ready for reproduction by line plate.

It is an object of this invention to provide the artist with an automatic method for achieving tone separation, and enabling him to create in a given illustration a combination of desired tints, double tones, stipples,

2,767,093 Fatented Oct. 16, 1956 etc., according to his choice, suitable for reproduction in printing presses without the need of hand work.

further object of this method is to improve in quality on previous semi-mechanical shading methods and to reproduce the most delicate shadings and tone differences.

A further object of the invention is to provide means for accenting the various tone patterns, so that the parts to be rendered in dots may have a gradation of different sized dots comparing to the gradations of the original, and the parts to be rendered in lines in the same illustration may have the lines running from thin to heavy in the same manner as is accomplished by varying the pressure applied to a pen in shading by hand.

is another oblect of this invention to enable the artist ographs and also combining them with type and other indicia on one plate, without the necessity of stripping, etc., and without requiring the special equipment and high skill needed for conventional half-tone for use in printing publications, posters, instruction sheets, maps, pamphlets, and the like.

A further object is to provide a method of this character which can be practiced while using either a positive or a negative as the original from which a printing plate is pr cessed or prepared.

It is still another object of the invention to provide means for use in making color reproductions which eliminates the occurrence of mechanical diificulties, such as moire patterns which commonly result in using conventional screens, etc.

it is another object of this invention to provide a color reproduction method employing color and contrast correction work to eliminate the hand work, etching, etc., usually necessary in color reproduction.

inother object of this invention is to facilitate the soealled controlled photographic printing processes, such as gum, hichromate, oil, and Bromoil, printing and transfer, and to aid the photographer in producing photographic prints with novel and striking effects.

A further object is to provide a photo printing plate characterized by a plurality of different image and tone defining markings, each type of marking characterizing a given general tone value and the individual markings of each type graduated according to the range of variation of that general tone value.

it is not intended to restrict the applications of the method by the foregoing enumeration of objects nor by the following disclosures of preferred or illustrative procedures which merely show some of the many applications possible within the spirit and scope of the claims.

in the drawings:

Fig. 1 is a transverse sectional view of one means for practicing the method, taken on line 1-1 of Fig. 2.

Fig. 2 is a face view of a part of the apparatus shown in Fig. 1.

Fig. 3 represents an unevenly distributed source of light in the form of a continuous-tone greyscale or shadowwedge with values running gradually from block, solid or opaque through grey or translucent to white or transparent. The values correspond to the values of a photographic continuous-tone negative.

Fig. 4 represents a white line drawn on black background or a transparent line in opaque medium, in other words, a line having a certain exposure value or actinic value.

Fig. represents a photographic record of the white line illustrated in Fi 4, shaded by the tone-wedge or greyscale of Fig. 3, during an exposure on ordinary photographic film or'paper. t

Fig. 6 represents the same image combination as in Fig. 5, but recorded on contrasty photosensitive material and developed for contrast.

Fig. 7 represents an unsharp or vignetted line or pattern element capable of reflecting or transmitting light, or a line having a certain light or exposure value, said line being drawn or placed on a non-reflecting, non-light transmitting or non-light-emitting background. This line is grey or translucent and has an actinic value less than the line shown in Fig. 3 or Fig. 4.

Fig. 8 represents the image of the line shown in Fig. 7, as recorded on contrasty sensitive material in an exposure through the wedge illustrated in Fig. 3.

Fig. 9 represents a line as shown in Fig. 7, intersected by a series of lines or pattern elements characterized by a light value of more than the light value, or a density of less than the density, of the line which is being intersected.

Fig. 10 shows a photographic record of the intersecting lines illustrated in Fig. 9 in combination with the light and shadow values shown in Fig. 3 on contrasty material.

Fig. 11 represents the intersecting lines shown in Fig. 9, again intersected by a series of lines or by a pattern image having less shadow value or more light value than any of the previous intersecting patterns or lines. These patterns intersect each other but are not superimposed in regard to their values. The combined patterns represent a screen or pattern image. The patterns combined and placed within a substantially opaque medium form a usable photoscreen or pattern image member.

Fig. 12 represents the values of the tone-wedge shown in Fig. 3 recorded through or photographed in combination with the screen shown in Fig. 11 on contrast material. The recorded image is a screening, pattern image member or a screened positive print made from the negative continuous light and shadow values as shown in Fig.

Fig. 13 represents the reversed values of the tonewedge shown in Fig. 3. it represents the values of a photographic positive print made from the values of Fig. 3 used as a negative. it also represents an optical or positive photographic image.

Fig. 14 represents the reversed values of the screen shown in Fig. 11, or a photographic print made on ordinary, not contrasty sensitive material using the screen as a negative. it also represents the screening as illustrated in Fig. 12, without the modifying influence of the light and shadow values of the tone-wedge during the exposure. it also represents a photoscreen or pattern image member useful in making screened lithographic negatives from continuous-tone positive images having continuous or graded tone-values.

Fig. 15 represents a photo-record of the wedge shown in Fig. 11, in combination with or recorded through the screen shown in Fig. 14. It represents a screened negative or negative photo-screening of the light and shadow values shown in Fig. 13.

Fig. 16 shows a print made from the screening illustrated in Fig. 15, made on contrast material such as for instance a lithographic albumen plate. Intermediate gradations have been eliminated in the process.

Fig. 17 shows a photoscreen combining a cross-hatch line pattern with one coarse and one fine stipple pattern.

Fig. 18 shows a photoscreen having both positive and negative patterns.

Fig. 19 shows examples of cuttings of line patterns.

Fig. 20 shows various densities of materials used to put into cuttings.

' Referring to the drawings, and particularly to Figs. 1 and 2, which illustrate one form of apparatus by which 'as described above, or in an enlarger or projector.

the invention may be practiced, the numeral 10 designates a light source associated with a contact printing apparatus 12. This contact printing apparatus consists essentially of a glass plate 14 and a backing plate 16. The original 18 of the photograph or other item to be printed, and which may comprise either a positive or a negative film, a painting of varying translucency, a color transparency or the like, is adhered to the glass plate 114, as illustrated in Fi 2, as by means of a pressure sensitive adhesive tape 20 or the like. The film 22 on which the image of the original is to be reproduced by my process is similarly applied by adhesive tape or the like to the backing plate 22. Film 22 may either be paper, film or a photographic plate, treated with a photographic emulsion of the contact or process type. Between the original 18 and the film 22 is interposed one or more pattern image members 24. Suitable means, not shown, are provided for maintaining register of the various parts and for supporting and positioning the pattern image members 24 between and in contact with the original 18 and the film 22.

For the practice of this method, one or more pattern image members 24 of each of two types may be provided. For use in working with a positive as the original, the pattern image member will comprise a transparent sheet of material, such as glass, photographic film, or the like, bearing opaque lines, stippling, etc., which is drawn, printed or otherwise applied thereto. Where photographic film is employed as a pattern image member, the lines, stippling, etc., may be photographically recorded on the film. Where lines are used, they are preferably close spaced, parallel and of selected width or weights. Thus the number of lines per inch may vary within a wide range from those which are comparatively few in number, as 40 per inch, to those of such number and fineness that they cannot be distinguished by the unaided eye, for example, 240 lines per inch. It will be understood, however, that the figures mentioned are merely illustrative and are not limiting with respect to either the upper or lower limits. Where stippling is used, a similar wide range of stippling efiects is possible. Consequently, the range of efiects which can be achieved by the process depends in part upon the number of pattern image members having patterns of difierent coarseness and fineness which are available to the artist.

Pattern image members for use in working from a negative film as the original are made of substantially opaque material having small transparent portions of desired design. For instance, a fogged film may have the emulsion removed, as by scratching the film, to produce the pattern image. Lines and stippled effects are preferred in such pattern image members in the same mannet as in the pattern image members for use with negative originals. Also, pattern images of different coarseness and fineness are desirable to increase the range of efiects obtainable.

It will be understood, of course, that the use of a contact printer 12 is merely illustrative, and that other apparatus, such as a camera, an enlarger or a projector may be used in practicing the method.

My new method is practiced as follows: The original continuous tone image 18, such as an object, a painting, a photographic print, a multitone photographic negative or a color transparency, etc., is placed in position to be photographed, either before a camera or, in the case of a negative or transparency, in a contact printer The film 22 to be exposed is then placed in its respective holder and in fixed position relative to the original in the apparatus, as upon the base 16 of the contact printer described above. A number of consecutive partial photographic exposures of the original are then made on the emulsion of film 22. Each exposure is made through a selected screen pattern formed by one or more pattern image members 24, said patterns preferably difiering for each exposure by using pattern images of different degrees of fineness so that each of these exposures correponds in value to a specir '3 tone of the original 18 to be renderd in the pattern selected therefor. The pattern image member or members 24 defining the selected pattern are used either in contact with the original It; or, as is preferred, in contact With the photographic emulsion or sensitized surface of film 22, in the event the apparatus employed, such as camera, enlarger or projector, does not permit contact of the pattern image memher with both the original 13 and film 22. The composite latent image obtained by these multiple exposures is then developed for contrast. On examination the developed image will be found to have been resolved into separate designs for each of its tone values, which is the result sought.

One specific procedure for practicing this invention, which is especially useful in working from positive copy, will now be described step by step. By this procedure a lithographic negative is produced in one process by using pattern images to produce, respectively, a single pattern for the light tones, two patterns overlapping for the middle tones, and three or more overlapping patterns for the dark tones. Also, clear whites and solid blacks are produced by this procedure.

1. The original 13 is placed on the copy board before a camera and properly lighted.

2. A sheet of litho film 22 is placed in the camera film holder, focused and well secured in position, as by tape 2i or other securing means.

3. The first of a set of three pattern image members 2 5 of the positive type, that is, opaque lines or other pattern on a transparent film or other base, is placed in close contact with the lithographic film emulsion and firmly secured in position, as by tape 20 or other means.

4. An exposure is made on film 22 though this pattern image member 24- long enough to record only the lighter tones of the original 18.

5. The second pattern image member 24, preferably having a pattern image of somewhat coarser texture than the first pattern image, is then superimposed the first pattern image member and secured in place. The lines of the second pattern image will preferably extend at an angle to the lines of the first pattern iriage.

6. A second exposure is now made through the two superimposed pattern image members onto the same photographic emulsion on film 22, long enough to record the medium tones of the original, i. e., for longer time than the first exposure.

7. The third pattern image member 24, preferably having a pattern image of still coarser texture than the first two and with a pattern depending on the final result desired, is now superimposed on the two previous pattern image members, taking care not to move the assembly of the first two pattern image members since it is important that each pattern image member stay in the same position throughout the series of exposures.

8. A third exposure is now made, this time through all three pattern image members onto the same photo graphic emulsion on film 22, long enough to record the dark grays, but not long enough to record those parts which it is desired to render in black or solid color in the final print.

9. The pattern image members are now removed from the emulsion and a final exposure made without pattern image members onto the lithographic film 22 which is still retained in its original position, long enough to record the highlights or those parts or" the original which it is desired to render in pure white on the final rint.

10. The sheet of litho film is now developed in the usual contrast developer.

The product of the above described procedure is a lithographic negative suitable for use in making printing plates, wherein the tone values of the original are rendered in separate and ditferent patterns, and which possesses zoos assembled or superimposed pattern image members, and

the pattern image members may be removed one by one between the successive exposures, taking care not to move the pattern image members which are to be used for the subsequent exposures. In the latter procedure the exposure time for each successive exposure is decreased according to the tones being rendered in each instance. This procedure is the reverse of that specifically described and brings about essentially the same result. Another alternative which possible is to use several pattern i rage members singly and in sequence before starting to assemble or superimpose the pattern image members. This will give the effect of subtracting these screen patterns from the following pattern and produces an effect similar to the effect obtained by scratching lines on a scratch board or Ross paper. The number of pattern image members employed may be limited to two; or more than three may be employed; and likewise the number of exposures may be three or more.

By the first method a screening or pattern image member may be formed in the nature of a photographic negative of the character illustrated in Fig. 15 of the dravings. considering this figure of the drawing and all other figures from '3 to 20, it should be observed that the weight or the lines plus the spacing of the lines indicates their relative opacity and translucency, that heavy lines close spaced indicate opacity, and light lines spaced far distant indicate translucency. Also the drawings utilize gradations in the weight and spacing of lines covering masses to indicate light and dark areas, the lightest areas being plain white, and the darkest of black being shown as solid black, and the weight and spacing of lines in between those shades indicating a density of color or darkness or color relative to the two extremes.

A second preferred method consists in following the same steps and procedure as outlir d in detail for the first method. in place of the original i ago however (Fig. 13 of the drawings) being photographed and constituting unevenly distributed light source, positive image, or light and shadow values or tone wedge, a blank drawing or white card is substituted representing an evenly distributed source of light, or one tone value. in this method the exposure times need not be changed, since only one tone value is being photographed. The difference in the time for which each pattern is used will create different densities in the intervening spaces between the individual pattern elements, provided the exposed sensitive material is developed for gradation and not for contrast. A not too contrasty sensitive material is recommended. The resultant multiple pattern image is illustrated in Fig. 11.

Tie white card is now removed from the copy board and replaced with a photographic continuous-tone negative made in conventional manner of the original image used in the first method. An exposure is now made on contrasty photo-sensitive material, such as the layers coated on litho film or photomechanical printing plates. Said exposure of the negative is made in combination with or through the values of the previously produced multiple pattern image or screen for a time sufficient to record the values of the negative through the values of the screen. The resultant screening after development for contrast is illustrated in Fig. 12, and is the equivalent to a photographic print or positive made from the negative screening or pattern image member produced by the first described method.

' A third method of procedure consists in following the procedure outlined in the second method up to the point where the multiple pattern image or screen, Fig. 11, has been produced. A positive print is then made from this negative combined pattern image or screen on ordinary photographic film, showing the gradations in reversed values, Fig. 14. The white card is now replaced by the original positive continuous-tone image as used in the first method on the copy board. The image and the produced positive pattern screen or member are then recorded in combination on contrasty material, exposure being made for a time sufiicient to record the light values of the original through the screen or combined pattern images. The resulting screening of tone values is the same as the screening produced by the first described method and illustrated in Fig. 15, namely a photomechanical screen negative rendering the tone values of the original continuous tone image in different pattern sections overlapping each other and covering areas of different dimension within the screened picture.

Thus it will be evident that a number of different types of effects and patterns may be secured, and screens or pattern image members of such types can be formed for simple and advantageous use for the purposes above mentioned.

The following explanation of the photographic principles involved, when considered with the drawings, will help to give a clearer understanding of the methods described and the screens or pattern image members and the resultant screenings of light and shadow values produced as set out above. Also, the explanation will show how these values are translated or transformed into pattern images, thus aiding the craftsman in producing the screens and screenings and in applying them to best advantage.

li a white line is drawn on a black background, as seen in Fig. 4, and photographed through a translucent gray-scale or tone-wedge, as shown in Fig. 3, and ranging in value from opaque through translucent to transparent, onto photo-sensitive material, the white line is recorded thereon, after development, as a black or solid line through the most transparent parts of the wedge, as a gray translucent line through the intermediate tone values and no record of the line is made or can be made through the densest or the opaque nonlight-transmitting parts of the tone-wedge. Fig. shows this result.

By using more contrasty sensitive materials and more contrasty working developers, the specific part of the line rendered as black or solid can be increased in length relative to the part rendered as grey or translucent. Fig. 6 illustrates this. By varying the light value or exposure value or" the line, the recorded part of line can be varied in length inversely proportional to the part not recorded, and the part rendered as gray or transparent can be further reduced or entirely eliminated in subsequent printing processes. For example, no gray or intermediate value is retained in photo-engraving, lithography or silk screen printing, whereas in photographic reproduction in gravure or dye transfer a certain amount of this gradation or softness may be retained if desired. Compare Fig. 12 and Fig. 16.

By varying the sharpness of outline of the line or pattern elements, the part recorded as solid on contrast material. can be made narrower or wider in accord with the superimposed densities of the tone-wedge, as seen in Pig. 8.

If the tone-Wedge itself is photographed through a memher of translucent lines, each line having a different density or light-transmitting value, the same result is achieved, namely, longer or shorter lines solidly recorded or rendered, the records of the densest lines being the shortest with equal exposure.

The single lines described may be multiplied to form series of lines or patterns, each pattern being characterized by a different light value or density. A contrasty photo record made of such overall patterns, in combination with a tone-wedge or an image having light and shadow values, will show greater or lesser segments or sections of each of said overall patterns as having been eliminated by the shadow values inherent in the gray scale or image. The segments recorded solidly will vary in area covered according to the values characterizing each pattern. The borders or limits of these sections will show a certain part thereof rendered as not solid or as grey or translucent according to the material used. For instance, inthe albumen of a lithographic plate the gradation would run from hard to soft, and in a gravure plate from deep to shallow.

In the past, patterns having different densities or actinic values have been combined to form photoscreens and also halftone images. However, the overall patterns have been superimposed, or in some cases juxtaposed, either in the photoscreens or during the screening of the halftone images. While such combinations prove valuable in the breaking up of images into half-tone patterns or dots, these combinations are not suitable to produce uninterrupted facsimile sections or reproduced segments of overlapping and intersecting shading patterns.

I have found that the pattern designs can be preserved in the final print, if the continuity of each pattern is preserved during the screening process. The three methods described show in detail how this is accomplished by placing or recording the pattern images in a mutually non-interrupting printing order.

I claim:

1. A photographic method consisting of recording a plurality of intersecting pattern images in photo sensitive material by successive partial exposures substantially in sharp focus on said photosensitive material with the employment of a plurality of pattern image members, each of said pattern image members having only two tones representing substantially complete opacity and substantially complete transparency, respectively, one of said part exposures being made by employing only one pattern image and another part exposure being made by employing a plurality of superimposed pattern image members including said one member, any pattern image member employed in more than one part exposure being held in the same position with regard to its exposure effect upon said photo sensitive material during each part exposure in which it is employed, each part exposure producing on said photo sensitive material a photographic impression retained during subsequent part exposures, one of said part exposures being of different exposure value than another as determined by the product of time duration of exposure and light intensity of exposure.

2. A photographic method as defined in claim 1, wherein the light value and the distribution of the light source over the pattern image members and the photosensitive materials during said one part exposure is different from another part exposure.

3. A photographic method as defined in claim 1, wherein the several pattern image members employed have dfierent sharpness of outline of the respective pattern design elements thereof constituting one of the two tones thereof.

4. A photographic method as defined in claim l, where in the several pattern image members employed respec tively have differently shaped pattern design elements thereof constituting one of the two tones thereof.

5. A photographic screening produced by the method defined in claim 1 and characterized by photographic values at intersections of photographic reproductions of said pattern elements which are substantially of the same tone value as the photographic reproduction of only one of said pattern elements.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Gerland Oct. 3, 1893 Larsen Jan. 11, 1916 Rowell July 25, 1933 Schupp Feb. 7, 1939 Schufftan Mar. 7, 1944 Corbett Aug. 6, 1946 Wattier Dec. 12, 1950 m 10 FOREIGN PATENTS Great Britain of 1903 Great Britain of 1904 Switzerland Jan. 27, 1905 Germany Nov. 16, 1935 OTHER REFERENCES Photographic Journal (Great Britain), March 1940, pages 59-64, pages 60-61 particularly cited. 

1. A PHOTOGRAPHIC METHOD CONSISTING OF RECORDING A PLURALTIY OF INTERSECTING PATTERN IMAGES IN PHOTO SENSITIVE MATERIAL BY SUCCESSIVE PARTIAL EXPOSURES SUBSTANTIALLY IN SHARP FOCUS ON SAID PHOTOSENITIVE MATERIAL WITH THE EMPLOYMENT OF A PLURALTIY OF PATTERN IMAGE MEMBERS, EACH OF SAID PATTERN IMAGE MEMBERS HAVING ONLY TWO TONES REPRESENTING SUBSTANTIALLY COMPLETE OPACITY AND SUBSTANTIALLY COMPLETE TRANSPARENCY, RESPECTIVELY, ONE OF SAID PART EXPOSURES BEING MADE BY EMPLOYING ONLY ONE PATTERN IMAGE AND ANOTHER PART EXPOSURE BEING MADE BY EMPLOYING A PLURALITY OF SUPERIMPOSED PATERN IMAGE MEMBERS INCLUDING SAID ONE MEMBER, ANY PATTERN IMAGE MEMBER EMPLOYED IN MORE THAN ONE PART EXPOSURE BEING HELD IN THE SAME POSITION WITH REGARD TO ITS EXPOSURE EFFECT UPON SAID PHOTO SENSITIVE MATERIAL DURING EACH PART EXPOSURE IN WHICH IT IS EMPLOYED, EACH PART EXPOSURE PRODUCING ON SAID PHOTO SENSITIVE MATERIAL A PHOTOGRAPHIC IMPRESSION RETAINED DURING SUBSEQUENT PART EXPOSURES, ONE OF SAID PART EXPOSURES BEING OF DIFFERENT EXPOSURE VALUE THAN ANOTHER AS DETERMINED BY THE PRODUCT OF TIME DURATION OF EXPOSURE AND LIGHT INTENSITY OF EXPOSURE. 